In a single-wafer type spin cleaning device (liquid processing device) configured to perform a liquid processing on a semiconductor wafer (hereinafter, referred to as a “wafer”) as a substrate, for example, an alkaline or acidic chemical liquid is supplied to the surface of the wafer while the wafer is being rotated such that the chemical liquid is spread over the surface of the wafer to remove, for example, dusts or native oxides, on the surface of the wafer. The chemical liquid remaining on the surface of the wafer is removed by, for example, a rinsing liquid. Then, when the supply of the rinsing liquid is stopped while the wafer is being rotated, the remaining rinsing liquid may be shaken off to obtain the wafer in a dried state.
However, according to a high integration or a high aspect ratio of a semiconductor device, a problem of a so-called pattern collapse has been increased, for example, in a process of removing the above described rinsing liquid. The pattern collapse refers to a phenomenon in which, when a rinsing liquid entering into a pattern is shaken off, the liquid remaining at the left and right sides of, for example, a convex portion of an unevenness which forms the pattern is unevenly dried, and then the balance of surface tension that pulls the convex portion in the left and right directions is lost and thus the convex portion is collapsed in a direction in which the liquid remains in a large amount.
As a method of removing a rinsing liquid remaining on a surface of a wafer while suppressing the occurrence of a pattern collapse, there is provided a technology of hydrophobizing the surface of the wafer so as to increase a contact angle between the wafer and the rinsing liquid, thereby reducing a surface tension which acts on a pattern (Patent Document 1).
In the technology disclosed in Patent Document 1, a wafer as an object to be processed comes in contact with a liquid of a hydrophobic agent to hydrophobize the surface of the wafer. Meanwhile, since some hydrophobic agents are expensive, there are attempts to hydrophobize the surface of the wafer by using a vaporized hydrophobic agent or a gas including mists of a hydrophobic agent (hereinafter, referred to as a “hydrophobic gas”) so that the amount of a hydrophobic agent to be used is reduced (Patent Document 2).
The inventor has developed a technology of hydrophobizing a wafer surface by using a hydrophobic gas, and newly has found that in some cases, the wafer surface which has been processed by a hydrophobic gas and then rinsed is contaminated with multiple particles.